1. Field of the Invention
The present invention relates to a thin film magnetic head for use with magnetic recording systems, and, more particularly, to a thin film magnetic head in which a recording head and a reproducing head are formed integrally with each other.
2. Description of the Prior Art
A prior inductive head produces a reproducing output proportional to running speeds of a recording medium.
On the other hand, a thin film magnetic head using the magnetoresistance effect is not dependent upon a relative speed between the head and a recording medium and produces a constant reproducing output such that the output is not reduced even when such relative speed is small. Accordingly, thin type of film magnetic head has been widely used with magnetic recording apparatuses in recent years. However, since such thin film magnetoresistive head is not capable of recording, they must be combined with an inductive thin film head of coil type in order to provide both recording and reproducing functions. An example of such this type of thin film magnetic head is disclosed in Japanese Patent Unexamined Publication Nos. 52-12814 and 61-48116.
In a prior thin film magnetic head, lower and upper magnetic layers are linearly extended in opposed relationship with each other on a substrate, and these magnetic layers and a magnetic gap formed therebetween constitute a magnetic circuit. In addition, a coil layer is formed around the magnetic circuit. The upper magnetic layer is divided into front and rear sections, and a magnetoresistive element is arranged to bridge these sections.
This thin film magnetic head acts in the manner described hereinbelow. In recording, a recording current flows through the coil layer, so that a recording magnetic field leaks to the outside through the magnetic gap, with writing on a recording medium being performed by the thus leaking magnetic field.
In reproducing, a signal magnetic flux generated from the recorded medium passes through the magnetic gap and the front section of the upper magnetic layer to flow into the magnetoresistive element. The signal is detected from the resistance change of the magnetoresistive element. More specifically, a sense current is applied to the magnetoresistive element and the resistance change of the element is transformed into a voltage change such that the signal is read out.
However, such prior thin film magnetic head can not provide favorable recording and reproducing where the recording medium does not have good running accuracy because the track width is the same in recording and reproducing. More specifically, assuming that the prior thin film magnetic head has a recording and reproducing track width T.sub.1 and the recording medium has a running accuracy of a, the maximum running deviation in recording and reproducing will become 2a and the effective reproducing track width will become T.sub.1 -2a, which means reduction in the reproducing output.